Abstract P4-09-10: Nomogram for predicting lymph node involvement in patients with invasive micropapillary carcinoma of breast: A SEER population-based study

Background: Invasive micropapillary carcinoma (IMPC) is an unusual and distinct subtype of invasive breast tumor with high propensity for regional lymph node metastases. Because of its lymphotropic nature at initial presentation, IMPC is considered to have an unfavorable prognosis when compared with invasive ductal carcinoma (IDC). The aim of this study was to identify risk factors accounting for its lymphotropic features and to develop a nomogram to predict the probability of lymph node involvement in IMPC. Patients and Methods: A retrospective review of the clinical and pathology records was performed in patients diagnosed with IMPC between 2003 and 2014 from Surveillance, Epidemiology, and End Results (SEER) database. Training set comprised patients diagnosed between 2003 and 2009, while validation set included patients diagnosed thereafter. Ethical approval of the study was granted by the Institutional Review Board of Fudan University Shanghai Cancer Center. Multiple logistic regression analysis was conducted. A logistic regression model was used to construct the nomogram in the training set and then validated in the validation set. Nomogram performance was quantified with respect to discrimination and calibration. Results: Overall, 1407 patients diagnosed with IMPC were enrolled, of which 527 in training set and 880 in validation set. The demographic characteristics were comparable within sets. Larger lesion, younger age at diagnosis, black ethnic and lack of hormone receptor expression were significantly related to regional nodes involvement. The AUC of the nomogram was 0.735 (95 percent confidence interval 0.692 to 0.777), demonstrating a good prediction performance. A calibration curve for the nomogram was plotted to evaluate the agreement between actual (observed) outcomes and expected probabilities. The slope of the calibration curve was close to 1, which indicated excellent calibration of the nomogram. The performance of the nomogram was further validated in the validation set, in which AUC was 0.734 (95 percent confidence interval 0.701 to 0.767). Conclusions: The striking difference between IMPC and IDC remains the increased lymph node involvement in IMPC and therefore merits aggressive treatment. The nomogram based on the clinical parameters was established, which could accurately predict regional lymph node status. This nomogram would facilitate evaluating lymph node state preoperatively and thus treatment decision-making of individual patients, especially in neoadjuvant settings. Citation Format: Ye F, Hu X, Shao Z. Nomogram for predicting lymph node involvement in patients with invasive micropapillary carcinoma of breast: A SEER population-based study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-09-10.